Tillage implements, such as disc harrows, are known in agriculture for working the soil either following crop harvest or in preparation for spring planting. Typically, tillage implements work the soil at a depth of 4-6″ in an effort to turn over new soil and cover crop residue on the surface. This is sometimes known as conventional or primary tillage and is in marked contrast to secondary or conservation tillage.
Disc harrows normally comprise a plurality of concave disc shaped blades mounted on a common gang shaft suspended beneath a tillage implement frame. The entire shaft is mounted at an angle relative to the direction of travel of the implement. By setting the angle, a different degree of tillage can be obtained. Attempts have been made to mount these shaft using C-shaped springs in an effort to absorb impact from obstacles present in the field. However, since the entire shaft is forced to move upwardly and deflect when a single disc encounters and obstacle, the force transmitted to the frame is still substantial. This can result in damage to the blades, the shaft bearings, or the shaft mounting assemblies. As a result, farmers are normally required to operate disc harrows at slower speeds in the range of 3-5 mph.
An additional problem with disc harrows is that, due to the close spacing of the blades on the gang shaft, plugging of crop residue can occur between the discs. This impedes operation of the implement and requires the farmer to stop and manually clean out the space between the discs before continuing.
A conservation tillage implement, designed to work the soil at shallow depths has been designed with individually mounted coulter wheel assemblies that are staggered. This apparatus is described in a co-pending US patent application published Mar. 9, 2006 as US 2006-0048953. This implement is for minimum tillage, not primary tillage, and comprises straight coulter wheels that do not engage with the soil in order to turn fresh soil on to the surface, but rather cut through crop residue by riding along parallel to the direction of travel of the implement. The individually mounted coulter wheel assemblies each comprise a coil spring having a horizontal spring axis, as described in U.S. Pat. No. 6,412,571. Attempts to place concave disc blades suitable for use in turning the soil on this assembly have resulted in an off-axis load being imparted to the coil spring. This causes the spring to deflect during normal operation of the tillage implement and results in the blades adopting an orientation more parallel with the direction of travel of the implement. This impedes the ability of the blade to turn the soil, which generally requires an angle with respect to the direction of travel.
As a result, there remains a need for an improved tillage blade mounting assembly and for tillage implements comprising same.